Cellular energy-absorbing structure fastening device

ABSTRACT

Helmet (1) comprising: a shell (2); a head receiving system (3); at least one cellular energy-absorbing structure (4) comprising a plurality of interconnected open-cells (9) configured to absorb energy by deforming during an impact on the shell (2); at least one clamping device (5) comprising abase (6) and a counter-base (7) connected to each other by means of a stretchable elongated body (8) to forma a single piece sized so as to pass through at least one open-cell (9) of the cellular energy-absorbing structure (4), wherein the stretchable elongated body (8) is configured to appreciably and reversibly elongate with respect to its original length if pulled.

TECHNICAL FIELD

The present invention relates to the field of helmets with cellularenergy-absorbing structures. In particular, the present inventionrelates to the helmets using layered structures with relative movementbetween layers for reducing translational acceleration and angularacceleration of the brain.

BACKGROUND ART

In the state of the art several types of helmets are known: motorcyclehelmets, automotive race helmets, industrial safety helmets, bikehelmets, ski helmets, water-sports helmets, equestrian helmets, Americanfootball helmets, etc.

Traditional sport, car and motorcycle helmets comprise:

-   -   an outer shell, preferably a hard shell;    -   a protective liner matching with the shell and arranged inside        the shell;    -   a comfort liner for making the helmet much more comfortable when        it's worn by the user;    -   a retention system, generally comprising a strap and a        quick-release locking system.

Industrial safety helmets normally comprise:

-   -   a outer hard shell;    -   a harness connected to the hard shell.

The outer shell gives to the helmet a specific appearance and provides afirst protection against impacts. In the helmets having a protectingliner, the shell also contains the protective liner. The material of theshell can be a polymer such as PC (polycarbonate), PE (polyethylene),ABS (acrylonitrile butadiene styrene) or a composite material such asglassfibre or carbon fibre. Depending on the material, the shell isgenerally thermomoulded or thermo-formed, for example in bike helmets,or injection-moulded, for example in ski helmets.

Generally, the protective liner is made of a polymeric foam, like EPS(Expanded Polystyrene) or EPP (Expanded Polypropylene), and is used forabsorbing the energy generated during a collision. The EPS liner orlayer absorbs the energy of an impact through compression. Currently EPSis the most used material for absorbing the energy of an impact andemployed in most of helmets.

Alternatively, high-performance energy-absorbing material are known,such as the energy-absorbing material distributed with brand Koroyd®.This kind of cellular energy-absorbing material absorbs much more energythan traditional EPS/EPP liners when an impact load substantiallyorthogonal to the shell occurs. This kind of cellular material absorbsenergy through a progressive buckling of its cells.

The comfort liner can comprise pillows made of synthetic or naturalmaterial, which adheres or is connected to the internal side of theprotective liner. In this way, the head of the user is not in directcontact with the protective liner but with the comfort liner that ismuch more comfortable. Alternatively to the comfort liner, industrialhelmets have a harness, consisting of a system of straps made of wovenbands or polyethylene. A harness is a cheap solution for combining asystem for maintaining the helmet over the head of the wearer and asystem for absorbing part of the energy of an impact. The harnessabsorbs less impact energy than polymeric foam liners.

The retention system is used for maintaining the helmet in position onthe head of the user and can comprise a regulation device for regulatingthe tightening of the helmet on the head.

During an impact, for example due to a fall of a biker, the outer shellcan impact against an object, like the ground, in any direction and theimpact load has a normal component and/or a tangential component. Thetangential component can create a rotation of the skull with respect tothe brain, while the normal component can cause the skull fractureleading to death. Both kind of injuries are important and needs to bereduced as much as possible by the helmet.

In order to absorb both normal and tangential components of an impactload, the solutions available in the state of the art employ a devicefor absorbing the tangential component and a device for absorbing thenormal component. In particular, all known solutions do not connect themtogether.

For example, certain helmets manufactured by the company Smith™ comprisea cellular energy-absorbing pad of the company Koroyd® and a brainprotection system developed by the company MIPS®. The cellularenergy-absorbing pad efficiently absorbs the normal component of impactload, while the brain protection system efficiently absorbs thetangential component. The cellular energy-absorbing pad fits in an EPSliner and the brain protection system is connected to the same EPSliner, as described by the document EP2440082B1. Said cellularenergy-absorbing pad is not connected to said brain protection systemand consequently they work like independent devices and notsynergically.

Other solutions that solve only one of the problems of absorbing thenormal component or absorbing the tangential component of an impact loadare available. For example, the helmet described in the documentWO2016209740A1 comprises a protective liner split in two parts, an outerliner and an inner liner. The outer liner is connected to the innerliner through an elastic band, which allows relative movements betweenthe inner and outer liners. This feature allows to reduce rotational ortranslational brain injuries. This document provides a solution fordividing a protective liner in two parts for efficiently absorbingrotational acceleration due to the tangential component of an impactload, but neglects how to efficiently mitigate linear accelerationimparted by the normal impact component.

Another similar solution is provided in the document US10398187B1 whichdiscloses two liners interconnected from outside through adjustableretainers. Even the document WO2020245609 discloses a helmet wherein theinner energy-absorbing liner is anchored to the outer shell via aconnector.

Since the device for absorbing normal impact component does notcooperate with the device for absorbing the tangential impact component,the impact loads are not efficiently absorbed. Moreover, the deformationof the device for absorbing normal impact components can compromise thefunctionality of the other one, or vice versa. In this way, the devicestheoretically work efficiently, but in practice each one affects thefunctioning of the other.

Furthermore, all the available solutions for sport, motorcycle and carhelmets use polymeric foam liners, e.g. EPS or EPP liners, while theinternational rules are evolving in favour of more environment-friendlysolutions, which avoid or reduce these kinds of materials.

None of the available solutions provides helmets able to efficientlyabsorb all kind of impacts through an integrated solution that resultsin a cheaper, simpler and more environmentally friendly product.

SUMMARY

Said and other inconvenients of the state of the art are now solved by ahelmet comprising: a shell, at least one cellular energy-absorbingstructure, at least one clamping device and a head receiving system.Said at least one cellular energy-absorbing structure comprises aplurality of interconnected open-cells configured to absorb energy bydeforming during an impact on the shell; said at least one clampingdevice comprises a base and a counter-base connected to each other via astretchable elongated body to form a single piece. The stretchableelongated body is configured to pass-through the cellularenergy-absorbing structure. Wherein the stretchable elongated body issized so as to pass through one or more open-cells of the cellularenergy-absorbing structure and, optionally, through apertures in theshell and/or in the head receiving system. The stretchable elongatedbody is configured to reversibly elongate with respect to its originallength if tensioned. The one or more clamping devices allow to keep thecellular energy-absorbing structure connected to the shell and/or to thehead receiving system. Moreover, the stretchability of the stretchableelongated body allows a relative movement of the cellularenergy-absorbing structure with respect to the shell and/or the headreceiving system. In particular, the stretchability of the stretchableelongated body allows to both follow the movements of the cellularenergy-absorbing structure when it crumples and to compensate lateralmovements due to the tangential component of the impact load. Theclamping device so conceived can collapse and stretch so as to followany kind of deformation of the cellular energy-absorbing structure. Inparticular, the fact of being a single piece allows to guarantee astable connection between the cellular energy-absorbing structure andthe other elements of the helmet and simple and economic solution forachieving this result.

In particular, the stretchable elongated body can be configured to reacha maximum elongation comprised between 150% and 500% of its originallength, without breaking. The elongation of the stretchable elongatedbody is not the elongation that any material can have if pulled, but asignificant elongation that allows to pass the clamping device throughthe cell/s of the cellular energy-absorbing structure and to allowrelative movements of the cellular energy-absorbing structure withrespect to the shell/head receiving system. The term “original length”means the length of the stretchable elongated body before beingelongated, thus without any force applied. The term “maximum elongation”means the elongation at break of the stretchable elongated body in atensile test.

Moreover, the stretchable elongated body can be at least in part made ofan elastic or viscoelastic material. In this way, theelongation/shortening of the stretchable elongated body contributes toabsorb the impact energy, in particular that of tangential component.

Preferably, the cellular energy-absorbing structure can be an array ofenergy-absorbing open-cells interconnected via their sidewalls. Thisarchitecture of the cellular energy-absorbing structure is particularlyefficient in absorbing axial loads, thus loads substantially parallel tothe open-cells longitudinal axis. In particular, each open-cell can havean open base facing the shell and an opposite open base facing the headreceiving system. This arrangement of the open-cells allows to absorbmore efficiently the axial impact load through the progressive crumplingof the cells.

Alternatively, the cellular energy-absorbing structure can be a latticestructure comprising solid portions and open portions configured to forma network of interconnected open-cells. This architecture of thecellular energy-absorbing structure is particularly efficient inabsorbing loads coming from any direction. In particular, the cellularenergy-absorbing structure can be arranged so that one side of thestructure faces towards the shell and an opposite side faces towards thehead receiving system. In this way, the cellular energy-absorbingstructure is arranged between the shell and the head receiving system.

Advantageously, the compressive force required to collapse the clampingdevice along a direction can be lower than or equal to that required todeform the open-cells of the cellular energy-absorbing structure alongthe same direction. This means that the clamping device does not resistwhen the cellular energy-absorbing structure is compressed due to animpact load and the cellular energy-absorbing structure can becompressed as if there were no clamping devices.

Preferably, the shell can comprise only a hard shell or, alternatively,a rigid or semi-rigid outer shell and an inner shock absorbing linerconnected to each other. In the former case, the shell is constituted bya hard shell, as in the case of industrial helmets. In the latter case,the shell comprises an outer shell and an inner shock absorbing liner,as in the case of sport helmets. The inner shock absorbing liner ispreferably made of a polymeric foam and can comprise a pocket whereinthe cellular energy-absorbing structure is arranged. This pocket isconfigured to retain the cellular energy-absorbing structure withoutusing additional retaining devices. In this way, the cellularenergy-absorbing structure and the shell remain connected despite of theclamping devices/s.

Preferably, the head receiving system can be a harness system or acomfort system. Preferably said harness system or a comfort system canbe connected to the counter-base or base of the at least one clampingdevice. In this way, a correct positioning of the head of the wearerwith respect to the helmet is guaranteed.

Preferably, the base or counter-base can be connected to the shell or tothe head receiving system through connecting means. In this way, theclamping devices are attached to the shell and the cellularenergy-absorbing structure is attached to the shell via the clampingdevices. This arrangement applies both in the case of a shell comprisingonly a hard shell, and in the case of an outer shell with an inner shockabsorbing liner.

Preferably, the connecting means can comprise a Velcro layer, anadhesive layer or snap-fit connector/s for simplifying theinterconnection between the clamping device and the shell or the headreceiving system.

Alternatively, the stretchable elongated body of the clamping device/scan be inserted in a hole of the shell and the base or counter-base canabut against the external face of the shell. In this way, the base orcounter-base leans on the external surface of the shell and the rest ofthe clamping device clamps the cellular energy-absorbing structure tothe shell.

Advantageously, the base can comprise a low friction layer arranged onthe outer surface of the base or counter-base. In this way, the clampingdevice can slide over the outer shell or the inner shock absorbing linerwhen the cellular energy-absorbing structure compresses along anin-plane direction.

Preferably, the clamping device can comprise an exceeding portionconnected to the counter-base for pulling the stretchable elongated bodythrough the at least one open-cell. This feature allows to pull theclamping device and to force the passage of the stretchable elongatedbody and the counter-base through the at least one open-cell in order tobring the counter-base on the opposite side of the cellularenergy-absorbing structure with respect to the base.

Advantageously, the thickness of the cellular energy-absorbing structurecan be longer than the original length of the stretchable elongated bodyof the clamping device. This means that the clamping device is tensionedwhen the counter-base and the base are disposed on opposite sides of thecellular energy-absorbing structure. This characteristic allows toexercise a soft compression on the cellular energy-absorbing structurethat guarantee a firm connection of the cellular energy-absorbingstructure to the shell and/or head receiving system.

Preferably, the base can be rigid or semi-rigid in order to guarantee astrong anchoring to the cellular energy-absorbing structure if thecounter-base is pulled. More preferably said rigid or semi-rigid base isco-molded with the stretchable elongated body. This kind ofinterconnection makes the clamping device a single piece despite itsdifferent materials.

These and other advantages will be better understood thanks to thefollowing description of different embodiments of said invention givenas non-limitative examples thereof, making reference to the annexeddrawings.

DRAWINGS DESCRIPTION

In the drawings:

FIG. 1A shows a schematic view of a cross-sectioned helmet according toa first embodiment of the present invention;

FIG. 1B shows a schematic view of a cross-sectioned helmet according toa second embodiment of the present invention;

FIG. 1C shows a schematic view of a cross-sectioned helmet according toa third embodiment of the present invention;

FIG. 1D shows a schematic view of a cross-sectioned helmet according toa fourth embodiment of the present invention;

FIGS. 2A, 2B, 2C and 2D show a schematic view of a cellularenergy-absorbing structure and a clamping device respectively during theassembling phase, before being compressed, after a compression due to anormal load and after a compression due to an inclined load;

FIG. 3A shows the helmet of FIG. 1A when an inclined impact load hitsthe shell of the helmet;

FIG. 3B shows the helmet of FIG. 1B when an inclined impact load hitsthe shell of the helmet;

FIG. 3C shows the helmet of FIG. 1C when an inclined impact load hitsthe shell of the helmet;

FIG. 3D shows the helmet of FIG. 1D when an inclined impact load hitsthe shell of the helmet;

FIG. 4A shows an axonometric view of said second type of clampingdevice;

FIG. 4B shows an axonometric view of the clamping device of FIG. 4Aconnected to an outer shell;

FIG. 4C shows an axonometric view of the clamping device and the outershell of FIG. 4B wherein the clamping device is inserted in a cell ofthe cellular energy-absorbing structure;

FIG. 4D shows an axonometric view of the clamping device, the outershell and the cellular energy-absorbing structure of FIG. 4C wherein theclamping device clamps the cellular energy-absorbing structure to theouter shell;

FIG. 5A shows a side view of a clamping device shown in FIG. 4A;

FIG. 5B shows a cross-section of the clamping device of FIG. 5A;

FIG. 5C shows a top view of the clamping device of FIG. 5A.

DETAILED DESCRIPTION

The following description of one or more embodiments of the invention isreferred to the annexed drawings. The same reference numbers indicateequal or similar parts. The object of the protection is defined by theannexed claims. Technical details, structures or characteristics of thesolutions here-below described can be combined with each other in anysuitable way.

In the present description, for the sake of conciseness, the term“cellular energy-absorbing structure 4” is sometime abbreviated as“cellular structure 4”, as well as the term “inner shock absorbing liner2B” is abbreviated as “inner liner 2B” and the term “stretchableelongated body 8” is abbreviated “body 8”. Other similar abbreviationscan be present in the following description.

FIGS. 1 represent some embodiments of the helmet 1 according to thepresent invention. This helmet 1 comprises a shell 2, at least onecellular energy-absorbing structure 4, a head receiving system 3 and oneor more clamping devices 5.

As described in detail in the following, the clamping devices 5 areemployed to allow a relative movement between two parts of the helmet 1and contribute to absorb the energy related to this movement.

In particular, in the embodiment of FIG. 1A the clamping devices 5connect the cellular structure 4 to the shell 2. In the embodiments ofFIGS. 1B, and 1D, the clamping devices 5 connect the cellular structure4 both to the shell 2 and to the head receiving system 3. In theembodiment of FIG. 1C, the clamping devices 5 connect the cellularstructure 4 to the head receiving system 3 but not to the shell 2.

The clamping device 5 is configured to pass-through the thickness of thecellular structure 4, from side to side. The clamping device 5 comprisesa base 6, a counter-base 7 and a stretchable elongated body 8 thatconnects them to each other. The base 6 and the counter-base 7 areopposite to each other with respect to the cellular structure 4. Thestretchable elongated body 8 is sized so as to pass through oneopen-cell 9 of the cellular structure 4, as shown in FIGS. 1A, 1B, 1D,or through a plurality of open-cells 9, as shown in FIG. 1C. Thestretchable elongated body 8 cross-section is thus smaller than theopen-cell 9 cross-section.

The base 6, the stretchable elongated body 8 and the counter-base 7 aremonolithically connected or joined so as to form a single piece.

Preferably, the stretchable elongated body 8 is made of an elasticmaterial, for example rubber, thermoplastic polyurethane (TPU),thermoplastic elastomer (TPE), silicone or another elastomeric material.These materials allow an elongation of the body 8.

As shown in the embodiments of FIGS. 1A, 1B and 1D, the cellularstructure 4 comprises an array of energy-absorbing open-cells 9. Theseopen-cells 9 are connected to each other via their sidewalls 10.

The open-cells 9 are open at their ends so that each open-cell 9realizes a tube through which the air can flow. The open-cell 9 has acircular cross-section as represented in FIGS. 4 . Alternatively, thecross-section of the open-cells 9 can be a square, a hexagon, anon-uniform hexagon, a re-entrant hexagon, a chiral truss, a diamond, atriangle or an arrowhead.

The open-cells 9 of said array can be welded to each other via theirsidewalls 10. Alternatively, the tubes can be bonded by means ofadhesive layers interposed between adjacent sidewalls 10. This kind ofadhesive can be a thermo-adhesive material, thus an adhesive that atroom temperature is solid and becomes liquid e.g. above 80-100° C.Otherwise, the adhesive could also be a reactive adhesive or pressuresensitive adhesive.

When the open-cells 9 have a circular cross-section, the outer diameterof the circular cross-section can range between 2,5 and 8 mm, and thewall thickness of said open-cells 9 can range between 0,05 and 0,2 mm.

The array of energy-absorbing open-cells 9 can be configured to absorbthe energy through a plastic deformation of the sidewalls 10 of theopen-cells 9, wherein “plastic deformation” means that the sidewalls 10crumple irreversibly, or through an elastic deformation of the sidewalls10 of the open-cells 9. In the latter case, the deformation is almostcompletely reversible and the sidewalls 10 come back a shape equal tothe original one.

Alternatively, the open-cells 9 can be the cells of a lattice structure,as schematically shown in FIG. 1C. In this case, the open-cells 9 areconstituted by hollow portions defined by the solid portions 12 of thelattice structure. Substantially, the three-dimensional grid of solidportions 12 of the lattice structure defines a network of interconnectedopen-cells 9 (i.e. the hollow portions of the lattice structure),through which the air can flow. These open portions 13 of the latticestructure realize said open-cells 9. The lattice structure 4 can beconfigured to absorb the energy through a plastic or elastic deformationof the solid portions 12.

It's useful to clarify that a cellular structure 4 normally has not widecells, otherwise the energy-absorption is compromised and the cellularstructure 4 becomes too soft for absorbing compressive loads.Consequently, the clamping devices 5 comprise slender bodies 8 forallowing the insertion into said openings 11 and the passage through theopen-cell/s 9. If the energy-absorbing structure would be made of anexpandable foam, like in the prior art solutions, the hole for receivingthe plug could be sized at will. Vice versa, in the present solutions,the cellular structure 4 imposes the dimension of the connecting device5 and not conversely.

The cellular structure 4, both in the version having an array ofenergy-absorbing open-cells 9 and in the lattice structure, comprises asurface facing towards the shell 2 and a surface facing towards the headreceiving system 3, as shown in FIGS. 1 . These surfaces comprise aplurality of openings 11 of said open-cells 9. In any one of theseopenings 11, the connecting devices 5 can be inserted.

With reference to FIG. 1A, it's represented an industrial safety helmet1 comprising only an outer shell 2A. This outer shell 2A is a hardshell, thus a shell made of a rigid plastic so to resist impacts. Aplurality of clamping devices 5 are connected through connecting means15 to the inner surface of the outer shell 2A. These connecting means 15can be an adhesive layer attached to the outer surface of the base 6 ofthe clamping device 5 and to the inner surface of the outer shell 2A.Each clamping device 5 crosses the cellular structure 4 with itsstretchable elongated body 8. The stretchable elongated body 8 passesthrough one open-cell 9 of the cellular structure 4. The bases 6 of theclamping devices 5 lie on the outer face of the cellular structure 4,while the counter-bases 7 of the clamping devices 5 lie on the innerface of the cellular structure 4. In this way, the cellular structure 4is connected to the outer shell 2A, but relative lateral movementsbetween them are allowed, as shown in FIG. 3A. The helmet 1 alsocomprises a head receiving system 3, that in this case is a harnesssystem 3A. This harness system 3A is connected directly to the outershell 2A, as in the traditional industrial safety helmets, andguarantees a space between the head 25 of the wearer and the cellularstructure 4. Despite this embodiment refers to an industrial safetyhelmet, the same features can be used for realizing a different type ofhelmet.

With reference to FIG. 1B, it is represented a helmet 1 comprising anouter shell 2A and head receiving system 3 connected to each otherthrough clamping devices 5. The cellular structure 4 is clamped betweenthe outer shell 2A and the head receiving system 3 by means of theclamping devices 5. The clamping devices 5 are configured to pass withtheir stretchable elongated bodies 8 through respective holes 23 in theouter shell 2A and penetrate respective open-cells 9 of the cellularstructure 4. The clamping devices 5 are also configured to pass throughpassages of the head receiving system 3 so as that counter-bases 7 ofclamping devices 5 are arranged over the inner side of the headreceiving system 3. In this way, the head receiving system 3 remainsclamped between the counter-bases 7 and the cellular structure 4, andthe shell 2 remains clamped between the base 6 and the cellularstructure 4. In order to pass from an outer side of the helmet 1 (theouter face of the shell 2) to an inner side of the helmet 1 (the innerface of the head receiving system 3), the clamping device 5 is stretchedand its body 8 elongates. This elongation allows to create a preloadacting on the shell 2 and on the head receiving system 3, thuscompressing the cellular energy-absorbing structure 4 in-between them.This kind of helmet 1 allows relative movements of the head receivingsystem 3 with respect to the outer shell 2A and with respect to thecellular structure 4, as shown in FIG. 3B.

With reference to FIG. 1C and 1D, it's represented a helmet 1 comprisinga shell 2 composed by an outer shell 2A and an inner shock absorbingliner 2B. Vice versa, the embodiment of FIG. 1B, like that of FIG. 1A,has a shell 2 only consisting of only an outer shell 2A. From astructural point of view, since the embodiments of FIGS. 1A, 1B arebetter for industrial safety helmets, the outer shell 2A is thicker thanthat of the other embodiments. Since the helmets of the embodiments ofFIGS. 1C and 1D are suitable for sport helmets, the outer shell 2A canbe rigid, like in the motorcycle or automotive helmets, or semi-rigid,like in the bike or ski helmets.

The inner shock absorbing liner 2B is preferably made of an expandedfoam polymer, like EPS or EPP.

In the embodiment of FIG. 1C, the inner liner 2B comprises a pocket 14in which the cellular structure 4 is arranged. The pocket 14 is a recessof the inner surface of the inner liner 2B. This pocket 14 is shaped soas to be substantially complementary to the cellular structure 4. Inthis way, the cellular structure 4 is retained in the pocket 14 withoutadditional connecting means. The pocket 14 has inner mouth that issmaller than its bottom surface, consequently once the cellularstructure 4 is arranged in this pocket 14, it cannot come out. The outershell 2A and the inner liner 2B comprise a plurality of vents 28. A vent28 is an opening that allows an air transit from the externalenvironment to the head 25 of the wearer. The vent 28 crosses the outershell 2A and inner liner 2B up to the bottom of the pocket 14. Fromhere, the air can reach the head 25. The helmet 1 is thus permeable. Thevents 28 are arranged not in correspondence of the cellular structure 4,but in a further embodiment (not shown) they can be arranged incorrespondence of the cellular structure 4 so that an airflow cross allthe elements of the helmet 1. In this embodiment, the cellular structure4 is a lattice structure, as described above. The stretchable elongatedbodies 8 of the clamping devices 5 pass-through a plurality ofopen-cells 9 in order to come over from the opposite side of thecellular structure 4. The bases 6 of these clamping devices 5 stay onthe outer side of the cellular structure 4 and lie on it, while thecounter-bases 7 are arranged over the inner surface of the headreceiving system 3. Substantially, the stretchable elongated bodies 8cross the open-cells 9 and the head receiving system 3. In this way, thecounter-bases 7 lie on the inner surface of the head receiving system 3,as shown in FIG. 1C. In this version of the helmet 1, the clampingdevices 5 clamp the head receiving system 3 and the cellular structure 4together. Furthermore, the clamping devices 5 comprise respective lowfriction layers 26 arranged on the outer surfaces of the bases 6.

This low friction layer 26 can be made of nylon, polycarbonate or PTFEfor reducing the friction between the bases 6 and the bottom of thepocket 14. In this way, the cellular structure 4 can slide over theinner liner 2B. The head receiving system 3 of this embodiment is acomfort system 3B of a different type with respect to that of FIG. 1B.

With reference to FIG. 1D, it's represented a helmet 1 comprising ashell 2 having an outer shell 2A and an inner liner 2B, as describedabove. Some vents 28 cross the outer shell 2A and the inner liner 2B.The bases 6 of the clamping devices 5 are embedded in the inner liner2B, while the stretchable elongated bodies 8 protrude outside the innersurface of the inner liner 2B towards the inner of the helmet 1. Theclamping devices 5 comprise counter-base 7 shaped so as to cross slotsof the head receiving system 3 and expand once on the other side. Theconnection of the clamping devices 5 with the head receiving system 3 ofthis embodiment is similar to that of FIG. 1B.

The embodiment of FIG. 1D also comprises a spacer 27 for each clampingdevice 5. The spacer 27 is a ring of nylon or PTFE. The stretchableelongated body 8 of the clamping device 5 passes through the centralhole of the spacer 27. The spacers 27 are arranged so as to stay betweenthe inner surface of the inner liner 2B and the outer face of thecellular structure 4. In this way, the spacers 27 act as cushionsbetween the inner liner 2B and the cellular structure 4, allowing arelative sliding. In this embodiment, the head receiving system 3 canmove with respect to the cellular structure 4 and, together, they canmove relative to the inner liner 2B. Alternatively, instead of thespacers 27, the inner liner 2B of the embodiment of FIG. 1F can comprisea low friction coating arranged so as to face the cellular structure 4for reducing the friction between these two elements of the helmet 1.

In the FIGS. 2 is shown a clamping device according to the presentinvention and how it interacts with the cellular structure 4.

The clamping device 5 of FIGS. 2 comprises a stretchable elongated body8 that is attached to the base 6. Said stretchable elongated body 8comprises a counter-base 7 which acts as a retaining portion. Thestretchable elongated body 8 is made of an elastic material so that thestretchable elongated body 8 can get longer. The counter-base 7 isspaced from the base 6 and their distance corresponds to the length ofthe stretchable elongated body 8. This length is shorter than thethickness of the cellular energy-absorbing structure 4, therefore, theclamping device 5 has to be pulled as shown in FIG. 2A. The stretchableelongated body 8A comprises an exceeding portion 22 which extends beyondthe counter-base 7. In order to let pass the stretchable elongated body8 through one open-cell 9, the exceeding portion 22 is inserted in theopen base 11 of said one open-cell 9 and once, it comes over theopposite side of the cellular structure 4, the exceeding portion 22 ispulled as shown in FIG. 2A, until the counter-base 7, passing throughthe open-cell 9, comes out from said opposite side. The elasticity ofcounter-base 7 allows the passage through one open-cell 9 of theclamping device 5. At this point, the exceeding portion 22 is releasedand the elasticity of the stretchable elongated body 8 spreads thecounter-base 7 over said opposite side of the cellular structure 4. Inthis way, the clamping device 5 exerts a force that attracts thecounter-base 7 and the base 6 towards each other. After the positioningphase described above and schematically represented in FIG. 2A, theexceeding portion 22 is cut, e.g. with scissors, and the clamping device5 looks as in FIG. 2B. This kind of clamping device 5 can change itsshape and follow the deformations of the cellular structure 4. Forexample, in FIG. 2C a force F is applied orthogonally to the cellularstructure 4 and the open-cells 9 axially crumple. In this case, thestretchable elongated body 8 relaxes, getting shorter. If the impactforce F is angled, as shown in FIG. 2D, the cellular structure 4 alsotranslates and slightly bends laterally. In this case, the clampingdevice 5 deforms, allowing this translation/deformation of the cellularstructure 4.

Alternatively, the stretchable elongated body 8 of the clamping device 5is made at least in part of a viscoelastic polymer. In particular, thestretchable elongated body 8 can be entirely made of a viscoelasticpolymer or can comprise an outer elastic portion inside which isarranged a viscoelastic material, for example a viscoelastic foam.

Advantageously, the stretchable elongated body 8 of the clamping device5 is configured to not impede the collapsing of the cellular structure4. In particular, the compressive force required to collapse theclamping device 5 along a direction X, as shown in FIGS. 2C, is lowerthan or equal to the compressive force required to deform the open-cells9 of the cellular energy-absorbing structure 4 along the same directionX.

In the FIGS. 3 , the helmets 1 of the embodiments of FIGS. 1 arerepresented during an impact with an inclined force F hitting the outershell 2A.

In particular, in FIG. 3A is represented the helmet 1 of the embodimentof FIG. 1A during an impact. The impact is represented through aninclined force F which causes a rotation R of the outer shell 2A withrespect to the head 25 of the wearer. A first portion of the impactforce F is absorbed by the harness system 3A which deforms prior thatthe head 25 reaches the cellular structure 4. Once the head 25 enters incontact with the cellular structure 4, the open-cells 9 crumpleabsorbing the normal component Fn of the force F. In the FIGS. 3 thecrumpling of the open cells 9 is represented through a reduction of thethickness of the cellular structure 4. Concurrently, the clampingdevices 5 laterally stretch allowing a relative movement of the cellularstructure 4 with respect to the outer shell 2A. The deformation(elongation) of the clamping devices 5 allows to absorb the tangentialcomponent Ft of the impact force F.

FIG. 3B shows the helmet 1 of the embodiment of FIG. 1B during an angledimpact with a force F which causes a rotation R of the outer shell 2Awith respect to the head 25 of the wearer. The deformation of thecellular structure 4 and of the clamping devices 5 is similar to thatdescribed for FIG. 3A. The open-cells 9 of the cellular structure 4axially progressive buckle absorbing the normal component Fn of theforce F and, in the same time, the clamping devices 5 bend and stretchabsorbing the tangential component Ft of the force F. The clampingdevices 5 hold the cellular structure 4 by means of the elongation ofthe elongated body 8.

FIG. 3C shows the helmet 1 of the embodiment of FIG. 1C during an angledimpact with a force F, which causes a rotation R of the shell 2 withrespect to the head 25 of the wearer. In this case, the latticestructure 4 slides over the bottom of the pocket 14 by means of lowfriction layers 26 arranged over the outer surfaces of the bases 6.Therefore, the cellular structure 4 deforms along both in-plane andout-of-plane directions. The cellular structure 4 hits against thesidewall of the pocket 14 and it compresses. The lattice structureslides in the pocket 14 deforming the solid portions 12 and absorbing agreat part of the tangential component Ft of the force F. Concurrently,the top-down crumpling of the open-cells 9 absorbs the normal componentFn of the force F. Moreover, the clamping devices 5 bend contributing toabsorb the tangential component Ft of the force F during the latticestructure deformation.

FIG. 3D shows the helmet 1 of the embodiment of FIG. 1D during an angledimpact with a force F which causes a rotation R of the shell 2 withrespect to the head 25 of the wearer. The deformation of the clampingdevices 5 together with the bending of the cellular structure 4 absorbthe tangential component Ft of the impact force F, while the normalcomponent Fn of the impact force F is absorbed by the axial progressivebuckling of the open-cells 9 of the cellular structure 4.

In particular, in FIGS. 4 is represented an exemplary embodiment of theclamping device 5 of FIGS. 3 . The clamping device 5 comprises a base 6monolithically connected to the stretchable elongated body 8, which inturn is a single piece with the counter base 7. This version of theclamping device 5 is represented in detail in the FIGS. 5 . Inparticular, from FIG. 5C appears immediately clear that the base 6 iswider than the counter-base 7. Indeed, the base 6 is often used asinterface for connecting other elements of the helmet 1, as shown inFIGS. 1A and 1C. In FIG. 5A, it's perceivable that the base 6 isslightly curved both on the inner and outer faces. This shape allows abetter fitting with the cellular structure 4 and with the shell 2.Moreover, the base 6 can be made of a different material with respect tothe elastic material of the stretchable elongated body 8, as shown inFIG. 5B. In particular, the base 6 can be made of a rigid plastic, likenylon, polycarbonate or ABS that is co-molded with the elastic materialof the stretchable elongated body 8.

The clamping device 5 of FIG. 4A is firstly attached to the shell 2, forexample with an adhesive layer (connecting means 15), as shown in FIG.4B. Secondly, the cellular structure 4 is arranged over the outer shell2A so that the stretchable elongated body 8 passes-through an open-cell9 and the exceeding portion 22 comes over the cellular structure 4, asshown in FIG. 4C. Thirdly, the exceeding portion 22 is pulled so thatthe counter-base 7 comes out the cellular structure 4. Once theexceeding portion 22 is released, the counter-base 7 pushes the cellularstructure 4 towards the outer shell 2A, as shown in FIG. 4D. Finally,the exceeding portion 22 is cut and the connection between the outershell 2A and the cellular structure 4 is realized in a quick and cheapmanner. The arrangement of FIGS. 4 corresponds to that of the embodimentshown in FIGS. 1A and 3A.

In the embodiment of FIGS. 4 , the cellular structure 4 is an array ofenergy-absorbing open-cells 9, but the same applies in case of a latticestructure.

All the features described for the embodiments of FIGS. 1 , can be mixedto obtain further embodiments not represented but included in thepresent invention.

Concluding, the invention so conceived is susceptible to manymodifications and variations all of which fall within the scope of theinventive concept, furthermore all features can be substituted totechnically equivalent alternatives. Practically, the quantities can bevaried depending on the specific technical requirements. Finally, allfeatures of previously described embodiments can be combined in any way,so to obtain other embodiments that are not herein described for reasonsof practicality and clarity.

LEGEND OF REFERENCE SIGNS

-   1 helmet-   2 shell-   2A outer shell-   2B inner shock absorbing liner-   3 head receiving system-   3A harness system-   3B comfort system-   4 cellular energy-absorbing structure-   5 clamping device-   6 base-   7 counter-base-   8 stretchable elongated body-   9 open-cell-   10 sidewalls-   11 open base of the open-cell-   12 solid portion of the lattice structure-   13 open portion of the lattice structure-   14 pocket-   15 connecting means-   22 exceeding portion-   23 hole in the shell-   25 head of the wearer-   26 low friction layer-   27 spacer-   28 vent-   F force-   Fn normal component of the force-   Ft tangential component of the force-   R relative rotation

1. Helmet comprising: a shell; a head receiving system; at least onecellular energy-absorbing structure comprising a plurality ofinterconnected open-cells configured to absorb energy by deformingduring an impact on the shell; at least one clamping device comprising abase and a counter-base connected to each other via a stretchableelongated body to form a single piece sized so as to pass through atleast one open-cell of the cellular energy-absorbing structure; whereinthe stretchable elongated body is configured to appreciably andreversibly elongate with respect to its original length if pulled. 2.Helmet according to claim 1, wherein the stretchable elongated body isconfigured to reach a maximum elongation comprised between 150% and 500%of its original length.
 3. Helmet according to claim 1, wherein thestretchable elongated body is least in part made of an elastic orviscoelastic material.
 4. Helmet according to claim 1, wherein thecellular energy-absorbing structure comprises an array ofenergy-absorbing open-cells interconnected via their sidewalls. 5.Helmet according to claim 1, wherein the cellular energy-absorbingstructure is a lattice structure comprising solid portions and openportions configured to form a network of interconnected open-cells. 6.Helmet according to claim 1, the clamping device is configured so thatthe compressive force required to collapse the clamping device along adirection is lower than or equal to that required to deform theopen-cells of the cellular energy-absorbing structure along the samedirection.
 7. Helmet according to claim 1, wherein the shell comprisesonly an outer hard shell.
 8. Helmet according to claim 1, wherein theshell comprises a rigid or semi-rigid outer shell and an inner shockabsorbing liner connected to each other.
 9. Helmet according to claim 8,wherein the inner shock absorbing liner comprises a pocket configured toretain the cellular energy-absorbing structure.
 10. Helmet according toclaim 1, wherein the head receiving system comprises a harness system ora comfort system.
 11. Helmet according to claim 1, wherein the base orcounter-base is connected to the shell or to the head receiving systemthrough connecting means.
 12. Helmet according to claim 11, wherein theconnecting means comprise a Velcro connection, an adhesive layer orsnap-fit connector/s.
 13. Helmet according to claim 1, wherein thestretchable elongated body is inserted in a hole of the shell and thebase or counter-base abuts against the shell.
 14. Helmet according toclaim 1, comprising a low friction layer arranged on the base orcounter-base of the at least one clamping device.
 15. Helmet accordingto claim 1, wherein the clamping device comprises an exceeding portionconnected to the counter-base for pulling the stretchable elongated bodythrough the at least one open-cell.
 16. Helmet according to claim 1,wherein the thickness of the cellular energy-absorbing structure islonger than the original length of the stretchable elongated body of theclamping device.
 17. Helmet according to claim 1, wherein said base isrigid or semi-rigid.
 18. Helmet according to claim 4, wherein eachopen-cell has an open base facing towards the shell and an opposite openbase facing towards the head receiving system.
 19. Helmet according toclaim 5, wherein the cellular energy-absorbing structure is arranged sothat one side of the structure faces towards the shell and an oppositeside faces towards the head receiving system.
 20. Helmet according toclaim 10, wherein said harness system or a comfort system beingconnected to the counter-base or base of the at least one clampingdevice.